Cheristin® starts killing fleas and protecting your cat in as little as 30 minutes and is effective for up to six weeks. Apply Cheristin® every month with our easy-to-apply tube with a round-tip applicator. How to apply Cheristin® on your cat in five easy steps: 1. Select a single tube of Cheristin® from the pack. 2. Hold the applicator tube upright and twist the nozzle tip to open. 3. Part the hair on your cat’s neck at the base of the head until skin is visible. 4. Place the tip of the tube directly above the skin and squeeze 2-4 times to dispense the contents directly on the skin. 5. Discard empty applicator tube in the trash.